1. Field of the Disclosure
This disclosure relates generally to oilfield downhole tools and more particularly to speed control for turbine drives.
2. Description of the Related Art
To obtain hydrocarbons such as oil and gas, boreholes or wellbores are drilled by rotating a drill bit attached to the bottom of a BHA (also referred to herein as a “Bottom Hole Assembly” or (“BHA”). The BHA is attached to the bottom of a tubing, which is usually either a jointed rigid pipe or a relatively flexible spoolable tubing commonly referred to in the art as “coiled tubing.” The string comprising the tubing and the BHA is usually referred to as the “drill string.” BHA's, as well as other wellbore devices, may include a turbine drive to generate rotary power. This rotary power may be conveyed to a consumer; e.g., an oil pump or an alternator.
Variations in the operating conditions, which may be intentional or unintentional, can alter the fluid flow used to energize turbine drives. For example, an increase in fluid flow rate can increase turbine rotational speed. Some consumers of rotary power can be damaged when driven at an excessive speed. The present disclosure addresses the need for controlling the speed of turbine drives.